Roofs used to cover electric arc furnaces normally have a central aperture to position and move the electrodes, and an aperture placed at a peripheral position through which the fumes and volatile slag are expelled by means of intake conduits associated with intake and filter systems.
The intake conduits can have a first L-shaped segment, connected to the roof of the furnace, associated with one or more conduits downstream connected to the intake and filter systems.
These conduits normally have a system to cool the fumes which serves to lower the temperature of the fumes so that they reach the outlet to the atmosphere at a lower temperature.
Moreover, a reduction in the temperature of the fumes makes it possible to use cheaper intake and filter systems as well as to reduce wear on the said systems during operation.
The cooling is usually achieved by means of the circulation of water in the appropriate pipes placed inside the intake conduits.
Cooling devices known to the state of the art provide a spiral shaped pipe, in which the cooling liquid flows, arranged around the periphery of the intake conduit.
The spiral shaped pipes known to the state of the art have their turns in contact with each other and attached to each other in such a way as to form a single rigid structure confining the intake conduit inside.
Therefore these structures have a configuration which implies a considerable volume of work, with regards to the heat flow exchanged, which is concentrated on the inner surface in that their outer surface is not lapped by the fumes. Moreover, this type of structure has a low resistence to thermomechanical stresses because the lack of flexibility of its conformation, if subjected to sudden heat variations, causes stresses on the surfaces of the pipes which may lead to breakages.
According to another solution, in order to increase the resistence of the pipes, an insulating layer of refractory material is applied to the heat-absorbing surfaces of the pipes themselves, but this causes a considerable increase in costs. Moreover, deposits of slag may accumulate on this refractory layer, which cause incrustations and compromise the efficient expulsion of the fumes.
A further problem with conduits known to the state of the art is that welds are required to join individual elements in order to form a single pipe of the desired length.
These welds constitute critical points and create stresses along the pipe which may cause them to break, with the resulting dangerous and harmful spillage of water.